Preparation of stable polyvinyl butyral dispersions



Patented Sept. 23, 1952 PREPARATION or STABLE 'ROLYVINYL HUTYIt'AL msemtsrons William'iH. Brom1ey,:-.lr., West-"Springfield,'-Mass., :assignor ".to Shawinigan Resins Corporation, -:Springfield, ;Mass,, "a corporation; of .Massaehu- -*No"Brawing;-' Application number-7, 1949, r Serial No. 120,223

' mam relates to stable .aqueous dispersions ofgpolyvinyl :butyral dispersionseandca process forpreparingthesamen v This application is acontinuation-impart f my copending application, Serial 'No; 63,630 filed December 4, 1948, now I). S. 2,532,223.

Dispersions of 1 polyvinyl acetal resins are-particularly useful iii-strengthening, bfld i l .and bonding textile fabrics -and fibers. The dried films-have also found fayoninzthe coating field because of their abrasion resistance and flexibility. Until now,-ma1;1y=special fields. of application havebeen closed tothese dispersions because of the instability of thedispersion inthe presence of some electrolytes, .hard water and many of the common fillersiand extenders, The dispersions that are unstable undertheseconditions are generally stabilized with the ammoniumor alkali metal-salts of long chain fatty acids such as oleicor stearic acids formed in situ. In the presence of some acidic materials these emulsifying agents lose their effectiveness It has {been though thatit'he use of such; acids formed in situ were necessary to formdis persion by a phase inversion process. I

""It is the generalobject or thisinvention taprovide a process for preparing stable aqueouls dia persions of polyvinylbutyral. Apartioular obgiect Tof lth-isuinvention is to ,prepare polyvinyl invert to a resin-in-water dispersion.

' This process may 'be'carried out in light-weight 7 equipment andwith relatively low power consumption. The following examples are;illustrafed-Claims. (Cuzco- 293) tive but are. not to be construed as indicating Exam le 1 900 parts of 218 centipoise polyvinyl butyral (1.5% acetate groups calculated as polyvinyl' acetate,*20 hydroxyl groups-calculated asjpolyvinyl alcohol and'the balance polyvinyl butyral groups}, 280 parts of water, 76 parts dod'ecyl benzene sodium sulfonate, and 310 parts of-butyl ricinole'ate are added to a standard Werner -Pfleiderer Jmi-xer equipped with sigma blades. The mixture is heated to about C. an-d agitated for approximately '10 minutes during which-time the resin becomes plasticized. "There- -after,--the=mixing iscontinuedto completely disperse' the==water throughout the plasticized mass. par'tsof water are then-added to cause the inversion of the water-in-resin dispersion to a resin-in-water dispersion. About 20 minutes are requiredtoinvert the 'dispersion. 1540 parts of water are then added to reduce the resin-in- -water dispersion"to-40% solids.

Examination of Y the product shows that the resinparticlesare below .5 micron diameter. Photographs. made in electron microscope studies ishownthat the 1great"majorityof the particles are below 1.1-micron in diameter.' The viscosity of this dispersion-is '400-500-':centipoises at '20 C. uThe dispersion of thisexa-mple can bediluted to -below .3% .soli'ds'swith hard water '(300p.-p.--in.') without precipitation of the internal phase} The pH-nf-the diluted dispersion can be reducedi-b'e- -low:.7.0. :This dispersion ::wil1 tolerate-IO times emore '.magnesium.- sulfate than .a similar dispersion made with;potassiumpleate; J

E xample-II -60 pounds of 'ISL- centipoise.polyvinylflbutyral 13% acetate groups calculated as polyviny1 acetate. 16.4% alcohol groups: calculatedas polyvinyl-alcoholand the balance polyvinyl'butyral) 27 "poundsof triethylene g lycol dihexoate,j5'.5 pounds of .de'cyl benzene sodium sulfonatejand -15 pounds -of-water are added 'toga'zor-gallon standard Werner-,Pneiqerer mixer. and processed as described in, Example I I This water-infplas- "tic1zedaresirie dispersion ;wi'l1' invert after thela'd "dition' of; approximatelyi29bj pounds or water or Katabout 67%"solids where the'deterg'enti ticizerare; figured as solids. f This dispersio withstandtinfinite*dilutionjwithoutprecipitat on,

.. iAn airgdried film j this dispersion 'is perfect- V clear"-=and transparent; fIt *ha's'a tensilestrength of between 3000 and 3400 pounds per square inch when measured on a film .020 inch thick. a

The addition of water solutions of partiallyhy- I Q d l yvi-nylv acetate did not disturb the stability of the dispe V The ammeter readings:

during the processing Numerous variations may be introduced into the [process as illustrated by the examples: in place of butyl ricinoleate and "triethyl'ene glycol dihexoate, used as plasticizers in the abov examples, other plasticizers forpolyvinyl butyral 1 may be used such as dibutoxy ethylEphthalate, castor oil, tricresyl phosphate, methyl ricinoleate, dibutyl phthalate, etc.

venient to add the plasticizer to the finished dispersion rather than to add it to the charge and thereby reduce the capacity of the mixingequipment. r

The polyvinyl butyrals which are usedu nficcordance with the invention may vary, substan tially in their composition. Thus, polyvinyl butyrals may be used which have up to 30% hydroxyl groups by weight, calculated as polyvinyl alcohol, up to 30% ester groups by .weight,.calculated as polyvinyl ester, and the balance substantially butyraldehyde acetalr Amongthe preferred embodiments are polyvinyl butyrals containing more than 5% and usually more than hydroxyl groups by weight, butnot. more than 25% hydroxyl groups, calculated as polyvinyl alcohol.

According to a further embodimentpf. the invention, the polyvinyl butyral contains 10% to 20% hydroxyl groups by Weight, calculated, as polyvinyl alcohol, less than 3% acetate groups by weight, calculated as polyvinyl acetate, and the balance substantially butyraldehyde acetal. The polyvinyl esters from which.;the polyvinyl butyrals are made may have widely varying degrees of polymerization as evidenced'by theviscosities of solutions thereof. For example, polyvinyl acetates may-be used whichgin l-molar benzene solutions have viscosities of from 5 to'500 or more centipoises at 20, C. Other polyviny esters may vary correspondingly.

The ester groups in the polyvinyl butyrals are usually acetate groups-but the acetate groups may be wholly or partially replaced by other ester groups suchas formate, propionate, butyrate, benzoate, etc. I

The amount of alkyl aryl s'ulfonatepsed depends upon the applicationfin which 'the dispersion is to be used, Below one part per .100 parts of polyvinyl butyral, the particle size is too large for some purposes and over parts causes no-further reduction in particle size but the excess aids in the stabilization of fillers and-e ftenders; Fillers and modifying agents are recom: mended for certain applications. starches, clays, natural gums and synthetic thickeners are -,used

The amount may be. varied from to 40% plasticizer on the solids basis. If more plasticizer is necessary for a pai' ticular formulation, it has been found more-con- 1 .1 5

4 dodecyl benzene sodium sulfonate in Example I. A similar product is obtained in each case.

The water added with the original charge reduces the tenacity of the plasticized resin and also partially plasticizes the polyvinyl butyral. The amount used can be asmuch as of the solids weight, but between 10% and 18% has .been found most suitable. If too much water is added it must be evaporated until the water-inresinlinversion point is reached. This inversion pointmust be determined for each change in the amount of plasticizer or surface active agent.

The foregoingdescription is given in illustration and-notin limitation of the invention as to aid-in the .a'pplicationor to vary thecha-racteristics of'the product. .Decyl ordodcyl, naphthalene sodium sulfonate. be substit ted for set forth in the appended claims.

What is claimed is:

1 1. A process for preparing a stable aqueous dispersion of polyvinyl butyral resin which consists-i'nmixing together at the same time 100 parts of unplasticized polyvinyl butyral made up on a weight basis of not over 30% hydroxyl groups calculated as polyvinyl alcohol, not over 30% ester groups calculated as polyvinyl ester and the balance substantially butyral acetal, 1.0 to 15 parts of an alkyl aryl alkali metal sulfonate, from 5 to parts of a plasticizer'for the polyvinyl butyral and an amount ofwater between 8% and 25% of the solids weight depending upon the amount of plasticizer and alkyl aryl alkali metal sulfonate used, agitating and heating the mixture until the resin is plasticized and a water-in-resin dispersion is formed, and then adding a sufl'icient amount of water with continued agitation to cause the dispersion to invert to a r'esin-in-watr dispersion.

2. A process as described in claim 1 in which the ester groups are acetate groups.

3; A process as described in claim 1 in which the polyvinyl butyral contains on a. weight basis from 5% to 25% ydroxyl groups and less than 3% acetate groups.

e. A process as described in claim 1 in which the alkyl aryl sulfonate is dodecyl benzene sodium sulfonate. I p

5. A process as described in claim 1 in which "the alkyl aryl sulfonate is decyl benzen e sodium sulfonate. ,7

fg. A process as described in claim 1 in which the "aryl sulfonate is decyl naphthalene sodium u iena ILL AM. H. BROMLEY, JR;

REFERENCES CITED Th e following references are of record in the file prisms patent:

UNITED STATES PATENTS:

, forHER REFERENCES ;Ind; ;& Eng.}-Qh e m., January194.3;page 12 6 I 

1. A PROCESS FOR PREPARING A STABLE AQUEOUS LDISPERSION OF POLYVINYL BUTYRAL RESIN WHICH CONSISTS IN MIXING TOGETHER AT THE SAME TIME 100 PARTS OF UNPLASTICIZED POLYVINYL BUTYRAL MADE UP ON A WEIGHT BASIS OF NOT OVER 30% HYDROXYL GROUPS CALCULATED AS POLYVINYL ALCOHOL, NOT OVER 30% ESTER GROUPS CALCULATED AS POLYVINYL ESTER, AND THE BALANCE SUBSTANTIALLY BUTYRAL ACETAL, 1.0 TO 15 PARTS OF AN ALKYL ARYL ALKALI METAL SULFONATE, FROM 5 TO 80 PARTS OF A PLASTICIZER FOR THE POLYVINYL BUTYRAL AND AN AMOUNT OF WATER BETWEEN 8% AND 25% OF THE SOLIDS WEIGHT DEPENDING UPON THE AMOUNT OF PLASTICIZER AND ALKYL ARYL ALKALI METAL SULFONATE USED, AGITATING AND HEATING THE MIXTURE UNTIL THE RESIN IS PLASTICIZED AND A WATER-IN-RESIN DISPERSION IS FORMED, AND THEN ADDING A SUFFICIENT AMOUNT OF WATER WITH CONTINUED AGITATION TO CAUSE THE DISPERSION TO INVERT TO A RESIN-IN-WATER DISPERSION. 